Pedicle Screw Assembly with Deployable Bone Anchors
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Solution Overview
Problem
Current pedicle screw fixation methods for spinal instability suffer from screw failure and pull-out, leading to pseudarthrosis and adjacent segment disease, with existing solutions like increased screw sizes, alternative thread shapes, and bone-cement augmentation being unreliable.
Innovation Solution
A pedicle screw assembly with integral bone anchors that extrude outwardly from the screw to engage the vertebra, providing additional anchoring within the bone tissue, and a method of deploying these anchors through channels in the screw to enhance fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If increased screw sizes are used to improve axial resistance, then pull-out resistance is improved, but surgical complexity and risk increase
Solution Approach 1:
The bone anchor is nested within the pedicle screw, with the anchor positioned inside the screw body and deployable through the screw tip. This nested configuration allows the anchor to provide additional axial resistance without requiring a larger external screw size, thereby maintaining surgical simplicity while improving pull-out strength.
Solution Approach 2:
The invention adds a radial dimension to the fixation system by deploying bone anchors outwardly from the screw tip into the vertebral body. This dimensional extension provides additional anchoring points without increasing the screw's primary dimensions, resolving the contradiction between strength and complexity.
2Strength
If alternative thread shapes are used to improve pull-out resistance, then axial strength is improved, but manufacturing complexity increases
Solution Approach 1:
The fixation system is segmented into two functional components: the pedicle screw with standard threading for initial fixation, and the separate bone anchor for enhanced pull-out resistance. This segmentation allows each component to be manufactured using standard, well-established processes, avoiding the manufacturing complexity of designing and producing screws with alternative thread shapes.
3Reliability
If bone-cement augmentation is used to improve fixation reliability, then pull-out resistance is improved, but surgical time and complexity increase
Solution Approach 1:
The bone anchor is pre-assembled with the pedicle screw before insertion into the vertebral body. This preliminary assembly eliminates the need for intraoperative bone-cement augmentation procedures, as the anchor-screw combination provides immediate mechanical interlocking and enhanced fixation reliability upon deployment.
Solution Approach 2:
The invention replaces the chemical bonding mechanism of bone-cement augmentation with a mechanical interlocking system. The bone anchor physically interlocks with the vertebral bone through its expandable or barbed structure, providing reliable fixation without requiring cement injection and curing time.
Data Source
AI summary
Various embodiments of a pedicle screw assembly disclosed herein include a pedicle screw configured for engaging with bone tissue. The pedicle screw includes a body defining a plurality of channels through the body of the screw and in communication with a plurality of respective distal openings defined along the screw body. The pedicle screw assembly further includes an anchor defining a plurality of anchor members which are configured to be received at least partially through the plurality of channels and the plurality of respective distal openings to further engage the pedicle screw to the bone tissue.